Changes

==Iron and Irrigation Technology==

Probably one of the most important developments to enable more advanced water technologies was the development and use of iron. In fact, the increasing sophistication of mathematics and engineering by the 1st millennium BC, along with iron technology, enabled the next major phase of development for irrigation technologies to occur. With the use of iron, rock could be excavated more easily. This facilitated the development of more sub-surface irrigation features, including tunnels and qanat systems (Figure 2), which were essentially tunnels with access holes that brought water from highland regions to lowland areas. These qanats also required a large amount of engineering, as channels had to be cut across mountains or difficult hilly areas, while channels were sometimes even cut from different areas and were met some place in the middle. Surface channels cut into mountain rock were now also developed, which allowed the capture of water from elevated regions. These technologies appear to have developed perhaps in Anatolia, Iran, or Arabia, although the origins are not completely clear. <ref>For more information on these Iron Age developments, see: Solomon, Steven. 2011. Water: The Epic Struggle for Wealth, Power, and Civilization. New York: Harper Perennial.</ref> In fact, what is significant about qanat systems is they enable the Iranian plateau to be densely populated, setting up the foundation of what would become a series of Iranian-based dynasties that occupied highland regions, such as the Achaemenids, Parthians, and Sasanians. In essence, water technologies altered the path of history, as it enabled a region once sparsely populated to become more central for large states and develop more dense populations. <ref> For more information on the role of qanats in developing settled societies and empires, see: Christensen, Peter, and Steven Sampson. 2016. Decline of Iranshahr: Irrigation and Environment in the Middle East, 500 BC-AD 1500. Copenhagen: Museum Tusculanum Press.</ref>

During the Iron Age (early 1st millennium BC), another important development occurred, which the development of aqueducts began to appear. In fact, the first aqueduct we know of developed in northern Iraq, just north of the city of Mosul. This aqueduct, part of a large canal system bringing water to the city of Nineveh, enabled water to be brought over different watersheds. In other words, it now allowed societies to build irrigation features that crossed natural elevation change that would have restricted where you could irrigate.

==Conclusion==